US Defense Secretary James Mattis told reporters that the purchase of Russia’s S-400 air defense systems by Turkey is a “sovereign” decision of the government in Ankara, reported RIA Novosti news agency of Russia.

STEPANAKERT, NOVEMBER 14, ARTSAKHPRESS:“That’s a sovereign decision for Turkey,” Mattis said. “Clearly, it will not be interoperable with NATO. So they’re going to have to consider that if they go forward.”

Press service of the Federal Service for Military-Technical Cooperation of Russia had informed in September that Moscow and Ankara had reached an agreement on the supply of S-400 air defense systems to Turkey.

And Turkish President Recep Tayyip Erdogan had stated that Ankara made the first respective payment.